SF6-SURFACE IONIZATION INDUCED BY INFRARED RADIATION(BA BEAM)

A CO2 laser-induced SF6 + Ba beam-surface ionization process has been studied in which vibrational excitation of SF6 molecules was carried o ut at the polished surface of polycrystalline Ba electrically heated t o 675 K. Both electron emission and negative molecular ion signal were detected. The dependence of the molecular ion signal on laser fluence and frequency (on SF6 molecular absorption) as well as on the SF6 gas pressure in the nozzle was studied. The results suggest a clear vibra tional selectivity, i.e., vibrational enhancement, of the SF6 + Ba bea m-surface ionization process. Several possible mechanisms for the nega tive molecular ion formation in the IR laser-induced beam-surface ioni zation process are discussed.